Since being scratched from the first four games of the season, Jack Hillen had become one of coach Scott Gordon’s most trusted defensemen and hadn’t missed a match.

That changed when Hillen took an Alex Ovechkin slap shot off of his face on Tuesday in a 7-2 loss. Considering the Capitals’ winger has one of the most dangerous shots in the league, it should come as no surprise that Hillen, who managed to skate off the ice with some assistance, suffered a broken jaw.

Hillen underwent surgery yesterday and will miss six to eight weeks as the Isles head out on a critical four-game road trip that starts tonight against the Hurricanes.

“Jack’s been playing some real good hockey for us, and for him to get hurt now [is tough],” Gordon said yesterday after most of the team went through off-ice drills before leaving for Carolina. “Especially since we rely on him for a lot of minutes in a lot of situations. He’s a key guy for us. But it could have been worse.”

Perhaps, but it’s still not exactly what the Islanders need as they continue to hover around the final playoff spot. Three of the teams they will face next — Philadelphia, Florida and Tampa Bay — are nearly in the same position.

“This is a huge trip for us,” Mark Streit said. “I just talked to a couple of the guys this morning about how big it is in determining which direction the team is going in.”

The Isles have had similar stretches this season and have survived them all. But they clearly would like to start making up some ground.

That will have to happen without Hillen, who, in the absence of the injured Radek Martinek, likely has become the Isles’ third best defenseman, along with Streit and Andy Sutton.

To take his place, the team called up Dustin Kohn, who made his NHL debut last week, when he filled in for the suspended Sutton and played reasonably well.

“I don’t know how long I’m gonna be here,” said Kohn, who got the call after playing in Bridgeport on Tuesday. “I have to take advantage of the opportunity. The more games you play, the better you feel.”

The Isles also could get veteran blue-liner Brendan Witt back. He skated again yesterday, but Gordon wouldn’t put a timetable on a potential return because Witt only has had one full practice since recovering from a calf injury. Witt said he hoped to be ready at some point on the trip.

Regardless of whom is in the lineup, the Isles can’t afford a drop-off as they head to the Olympic break.